(define strm123
  (stream-cons 1
    (stream-cons 2
      (stream-cons 3
        stream-null))))

(stream-car strm123) => 1

(stream-car (stream-cdr strm123) => 2

(stream-pair?
  (stream-cdr
    (stream-cons (/ 1 0) stream-null))) => #f

(stream? (list 1 2 3)) => #f

(define iter
  (stream-lambda (f x)
    (stream-cons x (iter f (f x)))))

(define nats (iter (lambda (x) (+ x 1)) 0))

(stream-car (stream-cdr nats)) => 1

(define stream-add
  (stream-lambda (s1 s2)
    (stream-cons
      (+ (stream-car s1) (stream-car s2))
      (stream-add (stream-cdr s1)
                  (stream-cdr s2)))))

(define evens (stream-add nats nats))

(stream-car evens) => 0

(stream-car (stream-cdr evens)) => 2

(stream-car (stream-cdr (stream-cdr evens))) => 4